This clinical study was approved by the ethical committee of the Medical University Innsbruck (1224/2020) and was conducted in accordance with the Declaration of Helsinki.
The tyrolean hip arthroplasty registry
The THAR is a regional arthroplasty registry of the Department of Clinical Epidemiology at the Tyrolean Federal Institute for Integrated Care (Tirol Kliniken GmbH, Innsbruck, Austria). Data from 10 hospitals that perform joint replacement surgeries within an area of 4880 square miles (12,650 km2) and covering a population of 757,634 (as of 31 December 2019) were recorded on the registry. The records start from the year 2004 and contain data on primary and revision arthroplasties of the hip. Demographic data, indications for surgery, name and type of implant, mode of fixation, and surgical approach are collected from the surgeon. Patients complete the self-administered Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) questionnaire 1 day before and 1 year after arthroplasty [13]. This registry annually covered around 2850 hip arthroplasties (primary and revision), and it was estimated that 97.5% of all primary arthroplasties performed on citizens of the region are covered. A recent estimation indicated that 171–210 elective hip arthroplasties are conducted per 100,000 inhabitants. The overall revision rate within 4 years after primary hip arthroplasty was reported as 4.12%. The self-reported level of adherence is 99.2%. The THAR deploys an internal validation process to ensure adherence and correctness are high, and data from medical insurers and the national death registry, as well as checks for plausibility, are embedded (Fig. 1).
Validation of the THAR
This study evaluated two consecutive series of patients who received primary total hip arthroplasty at our institution (BKH St. Johann, Tyrol, Austria) in the periods 2008–2012 and 2014–2016. Our institution is one of 10 hospitals that are covered by the THAR. It is located in proximity to the geographic state border. Only patients treated with a Siocon pressfit cup and a Monocon [18] or MonoconMIS [17] stem (Falcon Medical, Mödling, Austria) were included. Overall, a total of 1013 patients (corresponding to 1100 primary arthroplasties) met the inclusion criteria. The hospital records of those primary arthroplasties were gathered in a retrospective manner compared to the THAR.
The second part of this study included a prospective clinical follow-up of all included patients, with the aim to identify revision arthroplasties. According to their social security records, 125 patients had died following index arthroplasty. The medical files of the remaining 888 patients were obtained from our institution’s database. Patients were contacted by mail and phone and asked if they had undergone revision surgery. If patients reported revision surgeries that had been performed at external institutions, we requested medical records from the corresponding hospitals. A total number of 606 patients could be followed after a mean period of 8.05 years (standard deviation: 3.2). A total of 238 patients were lost to follow-up (response rate = 71.8%). Those revision arthroplasties were compared to the THAR.
Only the surgical report was considered proof of an arthroplasty. Adherence, completeness and correctness of the THAR were thereby assessed, both, for retrospectively identified primary arthroplasties and for prospectively confirmed revision arthroplasties [3].
Statistical analysis
Descriptive statistics were used to describe the dataset. Categorical values were presented as absolute and relative frequencies. Numerical variables were expressed as means, differences between groups have been compared with the student’s paired t-test. The level of significance was set at ≤ 0.05. In this study, the number of primary and revision joint arthroplasties was evaluated. The statistical evaluation has been performed using IBM SPSS Statistics version 27 (IBM, New York, USA).